In recent years, a typical frontier technology used in LCD manufacture industry is ODF (One Drop Fill). The ODF process specifically comprises dropping liquid crystals on one substrate (TFT or CF), uniformly coating sealing agent on another substrate associated therewith, and performing alignment with high precision to form a liquid crystal cell after coating and dropping processes has been carried out.
In current ODF coating process, distance between a coating nozzle and the glass substrate is very small and is only about 10 micron. Therefore, once foreign matter exists on a surface of the glass substrate or in a moving direction of the coating nozzle, the coating nozzle is inclined to be damaged by collision or to be blocked, as a result of which a break off of seal agent and a leakage of liquid crystal will occur and thus the coating nozzle has to be replaced, which in turn causes an increase of cost.